The performance monitoring of coordinate measuring machines is an issue of concern on a world wide basis. Coordinate measuring machines perform an important function in industrial quality assurance. Coordinate measuring machines are utilized to inspect the products of numerically controlled machine tools, as layout machines before machining, and to check feature locations after machining. Because of the need for accurate measurement of components produced, the coordinate measuring machine has become an important piece of equipment for both small job shops and large manufacturing plants.
Most coordinate measuring machine inspection systems are recalibrated periodically to verify compliance with original manufacturing specifications. Because this recalibration task demands activities that must be performed over a period of several days, recertification is often performed only after many months of multi-shift inspection use of the coordinate measuring machine. If the coordinate measuring machine system is found to be out of specification, a factory service representative is often needed to correct the evaluated source of tolerance deviation. In addition, the adjustment of the coordinate measuring machine can be an extremely time-consuming procedure. Finally, and of more importance to the coordinate measuring machine user, a product may have been inspected and possibly accepted by a coordinate measuring machine, for a long period of time, until the system is examined and found to be out of specification.
Many types of equipment are needed for the task of evaluating individual coordinate measuring machine conditions and their relation to possible inaccuracies experienced during inspection applications. In all cases, six degrees of freedom, including pitch, yaw, roll, horizontal and vertical straightness, and linear displacement or positioning performance of each linear slide are of importance. Furthermore, the relationship or squareness between each pair of axes must be evaluated and found to be within a specified tolerance band.
For a common three axes coordinate measuring machine a total of twenty-one individual sources of error may be specified. Additionally, long periodic errors of the displacement reading system, the hysteresis within the probing system, any backlash per linear axis, and deformation of the reference coordinate system through slide movement or temperature influences must be incorporated. Errors may also be based on the deviation of the comparator principle, often called the Abbe-offset. The influence of these errors forces the recertification task of a coordinate measuring machine to be time consuming, costly, and to require skilled personnel to perform.
Therefore, an object of the invention is to provide a device for evaluating the performance of coordinate measuring machines. This object may be achieved by providing a multi-coordinate measuring machine test standard capable of simply and accurately inspecting a coordinate measuring machine.